Textile fiber drawing device



Sept. 4, 1962 R. VIALLE TEXTILE FIBER DRAWING DEVICE Filed July 21, 1958ew. a

The present invention relates to devices for drawing textile fibers ofthe type comprising a feed station, a gripping station and a drawingstation proper, each of said stations comprising at least two rollers,namely: a lower positively driven roller and an upper pressure rollerfrictionally driven by the lower roller.

One object of the invention is to provide a drawing device of this typewhich is more reliable than the known devices and particularly one inwhich the danger of the fibers winding about the rollers is reduced to aminimum.

It is well known that the upper pressure roller of the drawing stationshould have a diameter at least equal to the mean length of the fibersin order to avoid the fibers winding about such roller which would bedetrimental to the operation of the drawing device. Actually, it hasbeen found that such windings are liable to occur should this rollerhave a diameter smaller than the mean length of the fibers.

Another object of the invention is to limit the diameter of the upperpressure roller of the drawing station to a value substantially equal tothe mean length of the fibers to be drawn.

Another object of the invention is to make the driving lower roller ofthe drawing station as large as possible within the limits of the spaceavailable. Such a disposition reduces the danger of the fibers windingabout the lower roller because the lower roller has a large diameterrelative to the length of the fibers and, the lower roller is thus muchlarger than the upper roller. Nevertheless if some fibers should windabout one of the rollers of the rawing station, such winding wouldlikely occur about the upper cylinder, which is much less inconvenientas is well known by those skilled in the .art.

A further object of the invention is to provide a drawing device inwhich the point of contact of the upper pressure roller of the drawingstation with the corresponding driving lower roller is spaced from thepoint of contact between both exit rollers of the gripping station by adistance substantially equal to the pinching length of the fibers to bedrawn. This pinching length is a feature well known in the drawingfield. It is substantially equal to the mean length of the fibers to bedrawn. If the sliver of fibers to be drawn was pinched between twopoints spaced apart by a distance greater than the mean length of thefibers, the latter would be pinched at one end only and run the risk ofbeing dissociated from the sliver subjected to the drawing operation. Asa contrast, if the fibers were pinched at two points spaced apart by adistance less than the mean length thereof, they would break.

The disposition which takes into account all three aforesaid features,is the only one allowing a lower roller much larger than the upperroller to be incorporated in the device without any detrimental effectupon the operation of the latter.

Still another object of the invention is to provide a drawing stationfurther comprising a second upper pressure roller arranged downstream ofthe first roller and larger than such roller. Such an arrangement, whichis known per se, combined with the disposition hereinabove indicated,improves the operation of the assembly because both pressure rollerspinch the sliver at two points respectively against the lower roller, sothat even though one of them happens momentarily to move away from3,051,97 Patented Sept. 4, 1962 the lower roller during operation, thesliver is kept pinched at the drawing station.

These and other objects of the invention will become apparent to thoseskilled in the art from the following description, taken in connectionwith the accompanying drawing the only sole FIGURE of which showsdiagrammatically and by way of example, one embodiment of a drawingdevice according to the invention.

In this drawing, 1 is a sliver of textile fibers to be drawn,principally cotton fibers, 2 the upper roller and 3 the lower roller ofthe feed station of a drawing device assembly. The sliver 1 passes firstbetween both rollers 2 .and 3 of the feed station with the roller 3being the driving roller and the roller 2 a pressure roller frictionallydriven by the roller 3. The sliver then passes to two rollers 5, 6 of agripping station against which rollers it is applied by a pressureroller 4-. At least one of both of the lower rollers 5, 6 is a drivingroller, whereas the pressure roller 4 is an idle roller.

At the exit from the gripping station, the sliver 1 passes through adrawing station proper comprising a driving lower roller 7 and two upperpressure rollers 8, 9. The point of contact A of the upper pressureroller 8 with the lower driving roller 7 is spaced from the point B ofcontact between rollers 4-, 6 of the gripping station, by a distancesubstantially equal to the pinching length of the fibers to be drawn.The diameter of the upper pressure roller 8 is substantially equal tothe mean length of the fibers, and the diameter of the lower roller 7 isas large as possible within the space available. In the embodimentillustrated, the diameter of the lower roller is much larger than thatof the upper roller 8 and, for instance, is substantially twice as longas the mean length of the fibers to be drawn.

It is known that drawing of the fibers is obtained by making the drawingrollers rotate with a surface speed greater than the surface speed ofthe gripping rollers. The ratio of these two speeds determines thedrawing rate. The winding risks, it will be understood, are maximum inthe drawing station; therefore it is particularly desirable to designthis station in the manner hereinabove described so as to materiallyeliminate these risks.

Finally, in the embodiment illustrated, the drawing station furthermorecomprises a second upper pressure roller 9, arranged downstream of thepressure roller 8 and of greater diameter than the latter.

Since the lower roller 7 of the drawing station cannot be increasinglylarge and since the diameter of the upper roller 8 cannot be reduced toa value shorter than the length of the fibers for the reason hereinaboveindicated, it will be readily understood that the aforesaid requirementsnamely the distance between the contact points A and B and diameter ofthe pressure rollers 8 being substantially equal to the length of thefibers, and diameter of the lower roller 7 being as large as possiblewithin the space available, are the only possible requirements forobtaining the most satisfactory results, as far as the reduction in thedanger of the fibers winding about the rollers is concerned.

The second pressure roller 9 has been provided for ensuring thecontinuity of the drawing operation of the sliver, even though, for anyreason whatever, the first roller should momentarily move out ofengagement with the lower roller 7. At this moment, the fibers which areno longer pinched at point A would be pinched at point C.

As many changes could be made in the above construc tion, and manywidely different embodiments of this invention could be made withoutdeparting from the scope of the claims, it is intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative and not in a limiting sense.

What I claim is:

1. In a sliver drawing mechanism having a positively driven lower feedroller, an upper feed roller with which said lower feed roller coacts,and an upper gripping roller, the combination with an upper drawingroller the diameter of which is smaller than the diameter of said uppergripping roller and is substantially equal to the mean length of thefibres of the sliver to be drafted, of a positively driven lowergripping roller coacting with said upper gripping roller and thediameter of which lower gripping roller is smaller than the diameter ofsaid upper drawing roller, and a positively driven lower drawing rollercoacting with said upper drawing roller and the diameter of which lowerdrawing roller is greater than the diameter of said upper grippingroller, said driven lower gripping roller contacting said upper grippingroller and said driven lower drawing roller contacting said upperdrawing roller at such points that the distance between said contactpoints corresponds substantially to the mean length of the fibres to bedrafted.

2. A sliver drawing mechanism as claimed in claim 1, wherein a secondupper drawing roller is located downstream of the first upper drawingroller and has a diameter greater than the diameter of the first upperdrawing roller.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Cotton Spinning, published in Washington, DC, by The TextileFoundation; copyright 193 8, see pp. 36 and 44. Copy in Division 21.

